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Influence of chemical reaction rate, diffusion and pore structure on the regeneration of a coked Al2O3-catalyst

Title data

Tang, Dahai ; Kern, Christoph ; Jess, Andreas:
Influence of chemical reaction rate, diffusion and pore structure on the regeneration of a coked Al2O3-catalyst.
In: Applied Catalysis A: General. Vol. 272 (2004) Issue 1–2 . - pp. 187-199.
ISSN 0926-860X
DOI: https://doi.org/10.1016/j.apcata.2004.05.040

Official URL: Volltext

Abstract in another language

As a contribution to a better basic understanding and an accurate modelling of the regeneration of coked catalyst particles, the following investigations were done with pure Al2O3 as a model catalyst: (1) determination of the intrinsic and effective kinetics of coke burn-off; (2) characterisation of the catalyst’s morphology with respect to the influence of the carbon load on the surface area, porosity, pore diameter, and tortuosity; (3) measurement of radial coke profiles within partly regenerated particles; (4) numerical simulation of the regeneration within coked particles and comparison with experimental data of radial coke profiles and the time needed for a certain degree of burn-off. For the modelling of coke burn-off within single particles, the chemical reaction rate, pore diffusion, radial gradients of the O2- and the carbon-concentration, and the influence of the carbon load on the porosity and tortuosity have to be considered. Only the resistances of external heat and mass transfer and of intraparticle heat conduction can be neglected, at least for particle sizes and temperatures of technical relevance for fixed beds (<5 mm, <700 °C). The measured and numerically simulated data according to this model presented in detail are in good agreement. The results show that temperatures above about 400 °C are needed to achieve regeneration within an acceptable timeframe. On the other hand, a temperature of more than about 500 °C will not anymore accelerate the burn-off, at least in case of fixed bed reactors with particles in the region of mm. This effect can be attributed to the increasing strength of pore diffusion resistance, and eventually the complete resistance is confined to the outer carbon-free shell.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: Pore structure; Regeneration; Coke burn-off; Tortuosity; Effective diffusion
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Chemical Engineering
Faculties > Faculty of Engineering Science > Chair Chemical Engineering > Chair Chemical Engineering - Univ.-Prof. Dr.-Ing. Andreas Jess
Faculties
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 540 Chemistry
600 Technology, medicine, applied sciences > 600 Technology
600 Technology, medicine, applied sciences > 620 Engineering
600 Technology, medicine, applied sciences > 660 Chemical engineering
Date Deposited: 24 Apr 2015 09:03
Last Modified: 24 Apr 2015 09:03
URI: https://eref.uni-bayreuth.de/id/eprint/10681